Differences In Dry Matter Yield Research Articles

Using a two-price market value framework to value differences in metabolizable energy concentration of pasture across seasons

CONTEXTInternationally, there have been focused efforts to develop methods of ranking pasture cultivars to assist livestock producers make informed decisions about investments in pastures. The Australian Forage Value Index (FVI) currently ranks cultivars for the dairy industry based on the value of differences in seasonal dry matter (DM) yield only. Metabolizable energy (ME) is the most important nutrient supplied by pasture for livestock production; its inclusion in the FVI may provide useful information for decision making. OBJECTIVEThe objective was to apply a two-price market value framework to value differences in both seasonal DM yield and ME concentration for valuing and ranking pasture cultivars. METHODSThe two-price market value framework allocates a replacement cost or salvage value to extra ME supplied by pasture during seasons when pasture is typically in deficit or surplus, respectively, of animal demand. The replacement cost and salvage value were calculated using a single (Method 1) or multiple (Method 2) nutritional components, and compared. The estimated market values for extra ME were combined with corresponding market values for extra DM yield and applied to a data set of 20 perennial ryegrass cultivars. Cultivars were ranked based on their extra annual market value compared to base cultivar Victorian. Rankings were first calculated based on the value of seasonal differences in DM yield, and then re-calculated using differences in both seasonal DM yield and ME concentration. RESULTS AND CONCLUSIONSReplacement costs of a MJ of ME of $0.023 and $0.010 were estimated for seasons of pasture deficit using Methods 1 and 2, with corresponding salvage values of $0.018 and $0.007 for seasons of pasture surplus. Compared with rankings based on the value of differences in DM yield alone, including the value of differences in ME concentrations had little effect on the rankings of individual cultivars. This result is strongly influenced by the fact that those cultivars that lead the ranking based on seasonal yield also have relatively high values for ME. SIGNIFICANCEThe two-price market value framework is one method for estimating the value of nutrients supplied by pasture and offers a simplified alternative to more common approaches for valuing pasture. The approach used here has potential for broader application and could be particularly useful for informing decisions about investments in research and innovation into traits which alter the nutritive concentrations of pastures swards and pasture species.

Impacts of Grazing on the Selected Features of Herbaceous Species and Harvested Dry Matter Yield of Natural Pasture

This study evaluated how grazing influenced the specific features of herbaceous species (basal cover, species richness, evenness, and diversity) as well as dry matter yield in the northwestern highlands of Ethiopia. For this study, the natural pastures were divided into three strata based on grazing types (grazing exclusion areas, controlled grazing, and continuous grazing). The areas in each grazing type were divided into two randomly selected (100 m × 50 m) sampling blocks. Then, each of the separated areas was divided into five 10 m × 10 m, and in each subdivided plot, (0.5 m × 0.5 m) were placed across the plots. Thus, a total of 30 (0.5 m × 0.5 m) quadrats were used to evaluate the effect of grazing on the basal cover, species richness, diversity, and dry matter yield of the herbaceous pasture layers. As the results showed, there were significant differences in dry matter yield, basal cover, species richness, evenness, and diversity among grazing areas. The dry matter yield, basal cover, species richness, and diversity were significantly (P<0.05) higher in both grazing exclusion and controlled grazing areas than in continuous grazing areas. Therefore, to increase the dry matter yield of natural pasture and to ensure sustainable livestock production, the livestock producers in the study areas should practice either a cut-carry system or a controlled grazing system.

Temporal changes in labile soil phosphorus pools in grassland receiving P recycled from dairy processing sludge

Replacing chemical fertilisers with recycled products will require new advice for phosphorus (P) use.. Emerging P fertilisers derived from dairy processing sludge (DPS) include products such as struvite and hydrochar. A field study monitored temporal changes in available, exchangeable, and Mehlich3 P pools in a P deficient grassland amended with DPS-derived hydrochar and struvite. Herbage P content and yields were compared with data from plots amended with a mineral P fertiliser. Regardless of fertiliser used, there was no statistical difference in dry matter yield. However, herbage P content varied depending on the fertiliser type. The optimal P content in herbage for cattle feed (0.3–0.4 %) was reached using struvite and mineral fertiliser. Application of struvites increased available, exchangeable, and Mehlich3 P, raising the available P levels to the agronomic optimal value for crop production (>5 mg l-1) within one month. In hydrochar amended plots, the optimal level of P was reached 4 months after fertilisation, at the end of the growing season. During the low growth or dormancy period, soil P levels decreased and remained low regardless of the treatment. In the struvite amended plots, available and exchangeable P pools recovered at the beginning of the second season. This effect was not observed in mineral fertiliser and hydrochar amended plots. A single application of struvite can replace mineral fertilisers supplying crops with P for more than one season. This needs to be reflected in the advice for growers to avoid excessive P application and legacy P deposition.

Efficacy of Different Fungicide Spraying Techniques on the Infestation with Kabatiella zeae and Formation of Fusarium Mycotoxins in Forage Maize

The application of fungicides in maize by the commonly used overhead spraying technique is more challenging than in small-grain cereals. Especially in later development stages, when the plant has reached a considerable height, lower plant organs (e.g., ears) may be insufficiently protected, since a large part of the applied fungicide is deposited on the upper leaves. In contrast, lower plant organs can be reached by the dropleg spraying technique, which allows sub-canopy applications. This study investigated the efficacy of fungicide applications during flowering in forage maize using the overhead and dropleg spraying techniques as well as a combination for the control of Kabatiella zeae and mycotoxin-producing Fusarium species, which can affect leaves and ears, respectively. The efficacy was evaluated in field trials under natural K. zeae and artificial Fusarium inoculum conditions in Northern Germany by measuring disease severities of K. zeae on maize leaves, dry matter yields, and concentrations of the Fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEN) at harvest. Fusarium inoculations of main ears at full flowering resulted in significantly higher DON and ZEN concentrations compared to natural Fusarium infections, whereas the dry matter yield was not affected. The strongest disease progressions of K. zeae were determined after flowering on the upper leaves and leaves around the main ear. Disease severities were significantly reduced on the upper leaves by the overhead application and the combination of the overhead and dropleg spraying technique, whereby the three spraying techniques were equally able to decrease the infestation on the yield-essential leaves around the main ear. No differences in dry matter yield were found between the application techniques, but they were significantly higher than in the untreated control. The contamination with DON and ZEN was most effectively reduced by sub-canopy applications using the dropleg technique, whether as a solo application or in combination with the overhead technique. The main ears were reached better with the applied fungicide, reducing Fusarium infections, and therefore, contamination with mycotoxins. The dropleg technique offers an opportunity for improved protection of lower plant organs, especially in tall growing crops. In combination with the overhead spraying technique, the protection of various plant organs along the entire plant with the applied fungicide could be advantageous, especially when different parts of the plant are affected by different fungal diseases.

FTC Based Forage Demonstration of Elephant Grass Technology in Ginchi, Wonchi and Debrelibanose District, Oromia National Regional State of Ethiopia

The study was conducted in three dairy potential areas of Ginchi, Wonchi, and Debrelibanose districts of Oromia region Ethiopia, to demonstrate promising elephant grass materials to smallholder dairy farmers. As a part of the methodology, a participatory extension approach is employed in this particular study to select a demonstration site. A total of 6 FTC were selected with an area of 10m2x20m2 plot sizes from each district. Elephant grass with accession numbers (14794) material as a candidate along with the check were demonstrated and evaluated for their biomass yield across tested sites. During the implementation phase, on-spot theoretical and practical training was provided to the smallholder farmers, development agents, and agricultural experts of the respective districts. The findings of this research revealed that there was a statistical significant difference in dry matter yield of demonstrated candidate material (accession 14794) over the local check at (p<0.01) probability level. And the dry matter yield of the candidate (accession 14794) ranged from 13.50 to 4.92 t/ha with a mean of 9.21 t/ha while the check provided 8.75 t/ha and 3.91 t/ha dry matter yield across the tested site. Moreover, Elephant/Napier grass materials responded differently across the tested sites because of differential responses of the climatic and biotic factors. The best average yield of the candidate (Accession #14794) were recorded at Ginchi district (10.40 t/ha) and followed by Debrelibanose district (8.87 t/ha) as compare to Wonchi district due to field management and another climate variability’s. Thus, the study recommended that it’s paramount to promote (accession#14794) elephant grass material with its recommended production package for further scaling up and popularization to the study area under similar agro ecology with the joint effort of district office of agriculture, non-government organizations and by other concerned stakeholders.

UAV-based prediction of ryegrass dry matter yield

ABSTRACT Forage yield is traditionally measured by manual harvesting, drying, and weighing and has multiple uses, including plant breeding and pasture management. The goal of this paper was to determine the accuracy of unmanned aerial vehicle (UAV)-based prediction of ryegrass percentage cover, vegetation volume, and dry matter (DM) yield in Autumn from 300 rectangular 1.5 m2 plots at a height of 20 m above ground level, compared to the current manual method. The secondary goal was to evaluate the UAV-based method for the determination of dry matter yield from five different ryegrass cultivars. A photogrammetry-based technique combined with a spectral method to determine the soil level was used to determine the percentage cover and vegetation volume of ryegrass plots, which were then used to obtain calibration curves to predict DM yield per plot. Calibration curves were obtained for five different ryegrass cultivars, with concordance between calibration curves for four of the five cultivar populations. The relationship between predicted forage volume (m3) and measured DM (g per 1.5 m2 plot) for ryegrass Populations 1,2,4,5 had an R2 = 0.61. Population 3 was different to Populations 1,2,4,5, with a two-fold difference in DM yield for the same forage volume. This demonstrated that 61% of the variance in DM yield can be explained by forage volume determined by a UAV-based photogrammetry method. We also further tested the methodology from 70 rectangular 2.4 m2 ryegrass plots in a Spring trial. The relationship between the predicted DM yield per 2.4 m2 plot (based on the average predictions from forage volume and forage area models) and measured DM yield per plot had an R2 = 0.66. UAVs can therefore increase the acquisition of field data for research studies and the management of pasture in grazed farm systems.

Cumulative Deficit Irrigation and Nitrogen Effects on Soil Water Trends, Evapotranspiration, and Dry Matter and Grain Yield of Corn under High Frequency Sprinkler Irrigation

HighlightsEvapotranspiration and corn grain yield under full and deficit water and nitrogen application were measured in a 3-yr study.Soil water trends, evapotranspiration, and dry matter and grain yields were significantly different between irrigation treatments and study year.Nitrogen availability did not significantly affect soil water trends or evapotranspiration within an irrigation level.Grain yield was not significantly different between full irrigation and 75% of full irrigation within a nitrogen level.Results indicate that crop evapotranspiration is independent of crop yield potential when soil water content is similar under high evaporative demand and frequent sprinkler irrigation.Reducing irrigation application to low-yield potential field areas will reduce yield.Abstract.Historically feed corn has been a minor crop in south central Idaho but over the past three decades corn production in southern Idaho has increased fourfold in response to a similar increase in the local dairy industry. Corn seasonal water use and response to water deficits in the region’s climate is lacking. A 3-year field study on corn (Zea mays L.) was conducted in 2017, 2018, and 2019 to evaluate the cumulative effects of continuous water and nitrogen (N) deficits on soil water trends, evapotranspiration, and dry matter and grain yield. Four irrigation rates, fully irrigated (FIT) and three deficit irrigation rates (75% FIT 50% FIT, and 25% FIT) combined with two N supply rates (0 and 246 kg N ha-1) were investigated under lateral-move irrigation. Growing season soil water depletion in 2017 in the 25% FIT and 50% FIT irrigation treatments significantly reduced soil water availability at planting in subsequent years and resulted in reduced yields relative to 2017. Nitrogen treatments had no significant effect on soil water availability, seasonal soil water depletion, or crop evapotranspiration (ETc) for a given irrigation treatment. Crop evapotranspiration was significantly different between irrigation treatments in each study year and decreased as irrigation amount decreased. Dry matter yield was significantly different between irrigation treatments in each study year, but there was no significant difference between the 75% FIT and FIT irrigation treatments for a given N treatment. Differences in dry matter yield decreased between N treatments as irrigation amount decreased. Grain yield was significantly reduced by deficit irrigation in each study year, but there was no significant difference between the 75% FIT and FIT irrigation treatments for a given N treatment in each study year. Grain yield was significantly different between nitrogen treatments for only the FIT irrigation treatment. The lack of significant difference in grain yield between the 75% FIT and FIT irrigation treatments resulted in a curvilinear convex downward water production function regardless of nitrogen treatment. A reduction in applied water resulted in a reduction of grain yield regardless of N availability suggesting that a reduction in irrigation application to less productive areas of a field will cause a yield reduction. The lack of significant difference in crop ETc between N treatments for a given irrigation treatment indicates that crop ETc is unaffected by crop yield potential when soil water contents are similar under high evaporative demand and frequent sprinkler irrigation. Keywords: Corn, Deficit irrigation, Evapotranspiration, Nitrogen, Sprinkler irrigation, Water use, Water production function, Yield.

Short-term impacts of winter bale grazing beef cows on forage production and soil nutrient status in the eastern Canadian Prairies

The impact of winter bale grazing on forage productivity and nutrient cycling was determined near Winnipeg, MB, Canada. Variable distribution of nutrients and forage yield within bale-grazed plots on a perennial grass–legume forage field was identified using an intensive grid sampling method. In bale-grazed plots, mean dry matter (DM) yield of forage decreased 68% in year 1 following bale grazing, with no difference in DM yield in year 2 following bale grazing, relative to an untreated control. Decreased yield was attributed to the large mass of waste feed and feces (21% of feed delivered) that remained at the centre of each bale-grazed plot, where each bale was placed. Concentrations of crude protein, total digestible nutrients, phosphorus (P), and potassium in forage increased in the first growing season following winter bale grazing compared with the control, particularly at the centre of each bale-grazed plot. Concentrations of residual nitrate-nitrogen and Olsen P in soil were 15 and 2.5 times greater, respectively, at the centre of the bale-grazed plots compared with untreated control plots. Dispersion of waste feed packs when bale grazing in subhumid climates on clay soils is recommended to minimize smothering and encourage rapid decomposition of waste feed and feces. Long-term studies are needed to determine the potential benefits and risks of bale grazing to forage productivity and soil nutrient status in the eastern Canadian Prairies.

NIVELES DE ABONOS FOLIARES EN EL RENDIMIENTO Y CALIDAD DE LA CHALA FORRAJERA (Zea mays) VARIEDAD CHUSKA BAJO LAS CONDICIONES EDAFOCLIMATICAS DE CAYHUAYNA 2017

With the objective of evaluating the effect of the levels of foliar fertilizers on yield and quality of forage chala was conducted this work of research, which was carried out on the grounds of the CIFO - UNHEVAL from the village of Cayhuayna. The parameters evaluated were: plant height at harvest, green forage yield, dry matter and protein content; for determination of dry matter was carried out in the Laboratory of Soil and Water of the UNHEVAL and the content of proteins, the samples were sent to the Laboratory of Bromatology of the UNAS. The results obtained were as follows: in plant height, treatments behaved similarly in their average, but treatment Biol 2.0 / 20 L obtained the highest with 2.88 meters; in green forage yield treatments EM 1 - activated 1.5 and 2.0 l / 20 L stand out with 106.06 and 100.65 t / has respectively; in the only dry matter yield differences 5% margin of error, where stressed treatment Biol 1.5 / 20 L with 30.42 t / ha; and in the protein content of maize chala EM and biological level of 2.0 L / 20 litres of water stood out with 9.0 and 9.2% respectively. Key words: forage, dry, protein, effective microorganisms, Biol

Niveles de abonos foliares en el rendimiento y calidad de la chala forrajera (Zea mays) variedad chuska bajo las condiciones edafoclimaticas de Cayhuayna 2017

Con el objetivo de evaluar el efecto de los niveles de abonos foliares en el rendimiento y calidad de chala forrajera se llevó a cabo el presente trabajo de la investigación, el cual fue realizado en los terrenos del CIFO – UNHEVAL de la localidad de Cayhuayna. Los parámetros evaluados fueron: altura de plantas a la cosecha, rendimiento de forraje verde, rendimiento de materia seca y contenido proteico; para determinación de materia seca fue efectuado en el Laboratorio de Suelos y Aguas de la UNHEVAL y para el contenido de proteínas, las muestras fueron enviadas al Laboratorio de Bromatología de la UNAS. Los resultados obtenidos fueron los siguientes: en la altura de planta, los tratamientos se comportaron de manera similar en sus promedio, pero el tratamien to Biol 2.0 / 20 L obtuvo la mayor altura con 2.88 metros; en el rendimiento de forraje verde los tratamientos EM 1 – activado al 1.5 y 2.0 L / 20 L destacan con 106.06 y 100.65 t/ha respectivamente; en el rendimiento de materia seca solo hubo diferencias al 5% de margen de error, donde destacó el tratamiento Biol 1.5 / 20 L con 30.42 t/ha; y en el contenido proteico del maíz chala el EM y Biol en el nivel de 2.0 L / 20 litros de agua destacaron con 9.2 y 9.0 % respectivamente.

Comparison of Energy Used and Effects on Bulk Density and Yield by Tillage Systems in a Semiarid Condition of Mexico

Energy used for tillage is an input with a high impact on the cost of crop production; it is desirable to till the soil using minimum energy. The objective of this study was to compare the specific energy expenditure, effect on soil bulk density, and forage yield of maize, by three tillage systems: Disk plow/Disk Harrow/planter (DDP), Chisel plow/Disk harrow/planter (CHDP) and No-Tillage (NT). Energy was measured for tillage operations in the summer season of 2013, 2016, and 2017. Bulk density in 2013 and 2016. Yield in 2013 and 2014. The variables of drawbar force (kN), working speed (m s−1), width (m), depth (m), fuel consumption (L ha−1), bulk density (g cm−3), and dry matter yield (Mg ha−1) were measured. Results showed that there were significant differences in the amount of energy used per ha; DDP used an average of 379.75 MJ, CHDP 135.01 MJ, and NT 26.43 MJ. The average energy applied to the soil mass for each system was 400 J kg−1 for DDP, 255.13 J kg−1 for CHDP, and for NT was 237.8 J kg−1. The overall energy efficiency was; 18.23% for DDP, 6.88% for CHDP, and 4.77% for N. The bulk density decreased significantly after three years for NT. There were no significant differences in dry matter yield. In the semiarid condition of Mexico, CHDP and NT are options for saving from 64% to 93% of energy, compared with DDP.

Summer production and survival of perennial ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea) genotypes in northern Victoria under differing irrigation management

Perennial ryegrass (Lolium perenne L.) is the predominant perennial forage species used in temperate irrigated dairy-production systems in Australia. However, when temperatures are high, even with optimal irrigation strategies and nutrient inputs, dry matter (DM) production can be compromised. This research investigated the effects of perennial ryegrass and tall fescue genotypes and summer irrigation on (DM) production and survival. Ten perennial ryegrass cultivars, three hybrid ryegrasses and two cultivars of tall fescue (Festuca arundinacea (Schreb) Darbysh.) were sown in northern Victoria, Australia, in May 2014, and were managed under full irrigation or restricted irrigation (no irrigation between late December and mid-March) over a 3-year period. Measurements included net pasture accumulation (DM production), sward density (plant frequency) and water-soluble carbohydrate concentration. Apart from the expected differences in DM yield over the summer period between full irrigation and restricted irrigation, there were few differences in DM production among perennial ryegrass or tall fescue cultivars. Plant frequency declined significantly under restricted irrigation in Years 2 and 3 compared with full irrigation but there were no differences among perennial ryegrass cultivars. In Year 2, plant frequency was higher in the tall fescue cultivars than the ryegrass cultivars. The recovery pattern in DM production following recommencement of irrigation in mid-March (autumn) varied across years. In Year 1, plants recovered rapidly once irrigation recommenced in autumn. However, in Years 2 and 3, autumn and winter pasture accumulation under restricted irrigation was 30–35% less than under full irrigation. These differences were possibly related to decreases in plant frequency, as well as to differences in the amounts of residual pasture mass (or carbohydrate reserves) present when growth ceased. Analyses of the water-soluble carbohydrate concentrations in the pseudostem during summer and autumn in Year 3 showed differences in total water-soluble carbohydrate and in fructan and sucrose concentrations between irrigation treatments but no consistent differences among genotypes.

Growth-Production Parameters of the First Slovak Cultivar of Festulolium A. et Gr.

The aim of this experiment was to compare growth and production parameters of the first Slovak cultivar of xFestulolium with Felina and Hykor. The experiment was conducted at the Demonstrating and research base of Department of Grassland Ecosystems and Forage Crops, Slovak Agricultural University in Nitra (Slovak Republic) with controlled moisture conditions (glass house) in 2017 (one year pot experiment). We compared new intergeneric hybrid Lenor with Felina and Hykor. In the experiment were evaluated average height (mm) and dry matter (DM) yields (g). New intergeneric hybrid Lenor was in every cut highest (P < 0.05) (59.57 mm) in compare with controlled varieties Felina (47.89 mm) and Hykor (47.07 mm). Lenor had higher dry matter yields than Felina and Hykor in the first and second cut. In the 3rd cut were not observed significant differences in dry matter yields. The highest DM yields were measured by Hykor (2.82 g). In sum of three cuts reached Lenor highest dry matter yield (4.99 g). This measured value was higher (P < 0.05) compared with Felina’s production.

Straw Yield and Quality: An Extra Motivation for the Introduction of Triticale in Mixed Farming Systems

Straw is a valuable by-product from cereal production. It is used for agricultural purposes as feed and bedding material for livestock. Additionally, cereal straw is a resource for the production of sustainable biomaterials and bio-energy. To meet the demands of these sectors substantial amounts of straw, with specific properties (e.g. water-holding capacity), are necessary. Since wheat breeding has mainly focused on grain yield rather than on straw yield other cereal species, such as triticale, can be of interest. Therefore, in this research the straw yield and water-holding capacity of four winter wheat and four winter triticale varieties were studied during two growing seasons. For both wheat and triticale there were differences in dry matter yield and percentage dry matter between growing seasons. Furthermore, depending on the growing season, there were significant differences in straw yield between the different wheat and triticale varieties. However, during both growing seasons, the straw yield obtained from the triticale varieties was significantly higher compared to the straw yield obtained from the wheat varieties. Concerning the water-holding capacity, it was concluded that the water absorption potential of triticale straw was higher compared to the water absorption potential of wheat straw. However, only in 2014 a significant difference between wheat and triticale was noted. So, it can be concluded that, besides the known advantages of triticale (performance on marginal soils, disease resistance, low fertilizer input, etc.), this crop has the potential to deliver high yields of high quality straw.

Centaurium erythraea Cultivation Method for Optimal Yield and Product Quality

ABSTRACTThe effect of cultivation methods on plant development, yield, secoiridoid glycoside content, and physical and microbiological contamination of centaury (Centaurium erythraea) were investigated. Plants were cultivated in uncovered soil, soil covered with mulch film, or in pots. There was no difference in dry matter yield of plants grown on a mulch film (665 g.m–2) and without mulch film (680 g.m–2), whereas the outdoor cultivation in pots resulted in lower yield (330 g.m–2). The physical and microbiological contamination was lowest in plants cultivated in pots and highest when cultivated without soil cover. The total concentration of secoiridoid glycosides in the plants was not affected by the cultivation methods. The use of mulch film combined high yield and low microbiological and physical contamination, and had no effect on the content of desired bioactive compounds.

EFFECTS OF NH4+–N/NO3−–N RATIOS ON PHOTOSYNTHETIC CHARACTERISTICS, DRY MATTER YIELD AND NITRATE CONCENTRATION OF SPINACH

SUMMARYMost plants prefer nitrate (NO3−–N) to ammonium (NH4+–N). However, high NO3−–N in soil and water systems is a cause of concern for human health and the environment. Replacing NO3−–N in plant nutrition regimes with an appropriate amount of NH4+–N may alleviate these concerns. The purpose of this study was to evaluate the effects of different NH4+–N/NO3−–N ratios on chlorophyll content, stomatal conductance, Rubisco activity, net photosynthetic rate, dry matter yield and NO3−–N accumulation in spinach grown hydroponically. The NH4+–N/NO3−–N percentage ratios were 0:100 (control), 25:75, 50:50, 75:25 and 100:0. Chlorophyll a and b, total chlorophyll, stomatal conductance, initial activity and activation state of Rubisco and net photosynthetic rate in spinach leaves were all reduced by increased NH4+–N/NO3−–N ratios. Significant correlation existed between these measurements. However, no statistical differences in dry matter yield were revealed between the 0:100 and 25:75 treatments. Leaf nitrate concentrations were reduced by 38% at the 25:75 treatment relative to the 0:100 treatment. These findings suggest that lowering the relative proportion of NO3−–N in fertilizer could effectively reduce NO3−–N contents in leafy vegetables without decreasing their yields.

Variation in N2 fixation and N contribution by 25 groundnut (Arachis hypogaea L.) varieties grown in different agro-ecologies, measured using 15N natural abundance

Groundnut (Arachishypogaea L.) is a major food legume in Africa, cultivated for its oil and dietary protein. This study evaluated 25 groundnut varieties for plant growth, N2 fixation, N contribution and soil N uptake at three differing agro-ecologies in South Africa, using the 15N natural abundance technique. The data revealed marked differences in dry matter yield, symbiotic N contribution and soil N uptake at each specific site. The percent N derived from fixation was 43–59% at Nelspruit, 47–67% at Mzinti, and 33–51% at Kliplaatdrift, amount of N-fixed was 76–188 kgha−1 at Nelspruit, 70–171kgha−1 at Mzinti, and 58–126kgha−1 at Kliplaatdrift, while soil N uptake was 58–152kgha−1 at Nelspruit, 45–121kgha−1 at Mzinti, and 71–135kgha−1 at Kliplaatdrift. There was a highly significant genotype×environment interaction, with the majority of groundnut cultivars obtaining more symbiotic N for their N nutrition at Nelspruit and Mzinti than at Kliplaatdrift. In fact, most groundnut varieties showed a decrease in shoot biomass, %Ndfa, and N-fixed at Kliplaatdrift possibly due to inhibition of N2 fixation by soil N. As a result, as many as 21 out of 25 groundnut cultivars derived more N from soil than from symbiosis at Kliplaatdrift. At Nelspruit, seven cultivars also took up more N from soil than symbiosis but still contributed significantly larger amounts of symbiotic N compared to Mzinti and Kliplaatdrift, an indication that those symbioses are relatively tolerant of soil mineral N, a trait highly desirable for agriculture and ecosystem functioning. Thus, plant growth and symbiotic functioning were strongly altered by mineral N uptake. As a result, there was a marked decrease in %Ndfa with increasing soil N uptake by groundnut at all study sites, especially at Kliplaatdrift (r=0.47***). There was also a significantly positive correlation between maximum temperature and dry matter yield (r=0.22*), as well as amount of N-fixed (r=0.20*). Rainfall also correlated positively with both dry matter yield (r=0.26*) and N content (r=0.40*), thus confirming the effect of genotype×environment interaction on plant growth and N nutrition. Taken together, cultivar ICGV03179 outperformed all the other genotypes in N2 fixation and grain yield at all three experimental sites, followed by varieties ICGV03157, ICGV00362 and ICGV99046, which also showed superior performance at two of the three locations.

Iron availability thresholds for the inoculation of cucumber with Trichoderma asperellum T34

AbstractInoculation with biocontrol agents can affect iron (Fe) uptake by plants. The objective of this research was to study the necessity of defining a Fe threshold in growth media for the inoculation with the biocontrol agent Trichoderma asperellum T34. A completely randomized experiment with cucumber (Cucumis sativus L.) was performed involving two factors: Fe rate in the growth medium in the form of ferrihydrite (0, 8, 16, 32.5, and 75 mg kg–1 of citrate‐ascorbate‐extractable Fe (CA‐Fe), and plant inoculation with T34. Dry matter (DM) of aerial parts of cucumber was decreased by T34. This was related to a decreased accumulation of Fe in plants, more in aerial parts than in roots. However, at the highest Fe rate (75 mg kg–1), differences in DM yield, plant height, and the content and concentration of Fe in shoots between inoculated and noninoculated plants were not significant. The threshold of CA‐Fe in the medium for DM yield of cucumber was 37 mg kg–1 without T34. With T34, this threshold was 65 mg kg–1, which implies that, below this limit, additional Fe supply is required for inoculation with T34.

Phosphorus application and liming effects on forage production, floristic composition and soil chemical properties in the Campos biome, southern Brazil

AbstractStudies of responses of native and introduced grassland species to lime and phosphorus (P) applications could contribute to improved understanding of the potential production of South American natural grasslands. To determine the effect of applying lime and different P sources on forage production, diversity and floristic composition, and on soil chemical properties, a small‐plot experiment was conducted over 12 years in natural grassland oversown with Lolium multiflorum and Trifolium vesiculosum in the Campos of southern Brazil. In treatments with soluble phosphate application, dry‐matter (DM) yield in November 2008, after 164 d of winter and early spring growth, increased from 2·3 to 3·2 t ha−1. Differences in DM yield in March 2009, after 111 d of growth during late spring and early summer, were not significant. The DM yield in April 2010, after 419 d of growth, increased from 7·7 to 9·2 t ha−1 in the treatments with P, regardless of the P source. Increased forage yield during the slow growth period in winter was only possible with the introduction of winter‐growing species (L. multiflorum and T. vesiculosum) and soluble phosphate application. Assessment of annual forage yield showed that the effectiveness of Gafsa rock phosphate was equivalent to that of soluble phosphates in the long term. Soluble phosphates and liming modified the botanical composition of natural Campos grassland in the long term, but floristic diversity was not altered.

Response of some Nitrogen fixing tree seedling to <i>Rhizobium</i> cross-inoculation

Six introduced and one native nitrogen fixing tree species were grown in a potted non-sterilized Inceptisol inoculated with: species-specific rhizobia strains; Rhizobium strain TAL 1145, a leucaena isolate; Bradyrhizobium japonicum strain TAL 169, and without inoculation. Twelve weeks later, significant species differences in dry matter yield, total N yield and nitrogen derived from the atmosphere (Ndfa) were obtained. Unlike earlier reports, Acacia albido and Acacia Senegal were better N2 fixers than Leucaena leucocephala . Two species did not respond to any of the inoculation treatments and none responded to inoculation with TAL 169. In species belonging to one cross-inoculation group, TAL 1145 had similar Ndfa values as those of species-specific rhizobia, implying that it is sufficient as the inoculum for this group.